Abstract: In a process for the afterburning of the combustible pollutants from an internal combustion engine, in order to automatically reduce the secondary induction rate when power increases without using a controlling valve actuated by the carburettor venturi depression, there is provided a volumetric efficiency of the secondary air pump linked to and activated by the engine and a volumetric efficiency which decreases when the ratio between its back pressure and suction pressure increases, this reduction being achieved through the proper selection of the pump volumetric comression ratio r: between 0.6 c and 1.3 c when a steeply decreasing trend is required, and above 1.3 c if a slower and slower decreasing trend is required. To perform this process an afterburner apparatus has a nitrogen oxide reducing catalyst placed inside the afterburner reactor on the gas stream immediately at the outlet of a torus, in which the gases are homogenized and their reaction with preinjection air is terminated.

Abstract: An apparatus for afterburning the combustible pollutants from the exhaust gases of an internal combustion engine in a reactor, in which secondary air is introduced. Upstream of the reactor, a chamber in the form of a torus is provided, through which the exhaust gases from a maximum number of cylinders flow before entering the reactor. A first obstacle, acting as a flame holder is disposed inside the torus. The reactor comprises a chamber whose inner surface is approximately a surface of revolution, and mounted inside of which is a second obstacle, acting as flame holder, substantially along the axis of revolution. The second flame holder has a diameter large enough to provide a contact time of 1 to 3 .times. 10.sup.-.sup.3 seconds of the gas flow in a recirculation zone surrounding the second flame holder, the diameter of the second flame holder being 15 to 40% of the reactor diameter.